Turbidity as a surrogate measure for total phosphorus concentrations in coastal streams in Östergötland (English)

Abstract [en]

Eutrophication is a major problem in the Baltic Sea, as a result of increased loading of nitrogen and phosphorus. In the coastal parts of Östergötland the soil largely consists of clay and contains high levels of phosphorus bound to clay particles. Erosion of the soil in agricultural areas makes the water turbid and transports phosphorus to the Baltic Sea. The aim of this project was to examine the relationship between phosphorus and turbidity in the coastal streams of Östergötland. The aim was also to evaluate the possibility to use turbidity as a surrogate measure for phosphorus. Water samples from 41 streams along the coast of Östergötland were collected once from each location 7 – 11 of April 2014. Variables examined were turbidity, total phosphorus, molybdate reactive phosphorus and water color (absorbance 420 nm). On average, particulate phosphorus made up 80 % of total phosphorus. The study showed a significant correlation between total phosphorus and turbidity (R2adj=0.879, P<0.01, linear regression). Water color was not correlated with total phosphorus. A multiple regression with turbidity and water color as independent variables resulted in a slightly improved model (R2adj = 0,886), but was regarded as not meaningful considering the additional efforts. The conclusion of the project is that is it possible to use turbidity as a surrogate measure in these streams.